Sniffer leak detector with multi-stage membrane pump

Abstract

A sniffer leak detector includes a mass spectrometer for analyzing hydrogen or helium, a turbomolecular pump which is connected with said mass spectrometer and whose outlet is connected with a prevacuum pump, and a sniffer probe which includes a plurality of intake lines and is connected with said inlet of said turbomolecular pump, wherein a vacuum pump includes at least three stages whose inlet stage defines said prevacuum pump and is connected with said outlet of said turbomolecular pump via a blocked throttle, wherein, between adjacent stages of said vacuum pump, an intermediate inlet each is provided, wherein each intermediate inlet is connected with a different intake line of said sniffer probe and at least one of the intake lines as a suction line is connected with said inlet of said turbomolecular pump for obtaining different gas flows.

The invention claimed is: 
     
       1. A sniffer leak detector comprising:
 a mass spectrometer for analyzing hydrogen or helium, 
 a turbomolecular pump which is connected with said mass spectrometer and whose outlet is connected with a prevacuum pump, and 
 a sniffer probe which comprises a plurality of intake lines and is connected with an inlet of said turbomolecular pump, and 
 wherein 
 a vacuum pump comprising at least three stages whose inlet stage defines said prevacuum pump and is connected with said outlet of said turbomolecular pump via a blocked throttle, 
 wherein, between adjacent stages of said vacuum pump, an intermediate inlet each is provided, wherein each intermediate inlet is connected with a different intake line of said sniffer probe and at least one of the intake lines as a suction line is connected with said inlet of said turbomolecular pump for obtaining different gas flows. 
 
     
     
       2. The sniffer leak detector according to  claim 1 , wherein the vacuum pump includes at least four stages, wherein two first stages are connected in parallel and define the prevacuum pump. 
     
     
       3. The sniffer leak detector according to  claim 2 , wherein the vacuum pump is a four-stage membrane pump whose outlet stage generates a gas flow in the range between 2000 and 4000 sccm and whose next-to-last pump stage generates a gas flow in the range between 200 and 400 sccm. 
     
     
       4. The sniffer leak detector according to  claim 1 , wherein the suction line is connected with the intermediate inlet via a blocked throttle. 
     
     
       5. The sniffer leak detector according to  claim 1 , wherein the respective pump stages are configured such that, in the intake lines, an intake flow is generated which is larger by at least a factor of 5 than a measuring gas flow branched off therefrom towards the turbomolecular pump and destined for the mass spectrometer. 
     
     
       6. The sniffer leak detector according to  claim 1 , wherein an inlet flow of the turbomolecular pump amounts to approximately 30-70 sccm. 
     
     
       7. The sniffer leak detector according to  claim 6 , wherein the inlet flow of the turbomolecular pump amounts to approximately 50 sccm. 
     
     
       8. The sniffer leak detector according to  claim 1 , wherein the suction line of the turbomolecular pump is provided with a blocked orifice which adjusts an inlet flow of said turbomolecular pump.